The fictional world where The Lord of the Rings film trilogy takes place is called Middle-earth.
Middle-earth is the setting for most of J. R. R. Tolkien’s major stories about the history of Arda. The films show only part of this much larger world, including the Shire, Rivendell, Rohan, Gondor, Mordor, and many regions between them. The plot follows the struggle to destroy the One Ring and defeat Sauron.
The name is sometimes misunderstood as meaning the entire planet. In Tolkien’s legendarium, Middle-earth is a region of Arda, the world in which the stories occur. It is also a translation connected to older Germanic and English ideas of a central inhabited world.
Middle-earth is not the same as Valinor, the western realm associated with the Valar and many Elves. Nor is it a name for Mordor alone. Mordor is one land within Middle-earth, while the trilogy’s journey crosses many different peoples and territories.